Sterilization of Bulk Storage Vessels with Chlorine Dioxide Gas - - PowerPoint PPT Presentation

Sterilization of Bulk Storage Vessels with Chlorine Dioxide Gas August 13, 2010

Sterilization of Bulk Storage Vessels with Chlorine Dioxide Gas

Presented By: Michael Burke Mark Morgan, Ph.D

What is Chlorine Dioxide - ClO2 ?

• Yellow to Greenish/Yellow Gas at Low Concentrations
• ClO2 is a strong oxidizer (similar to liquid bleach, NaClO)
• Can be corrosive at high concentrations (but less than

chlorine)

• Generated from Sodium Chlorite or Sodium Chlorate salt
• Dissolves quickly in water (Aqueous chlorine dioxide)
• Smells like chlorine (swimming pool)

Process Solutions

Uses of Chlorine Dioxide - ClO2

• Major Industrial uses –
• Pulp and Paper Bleaching (by far largest user of

ClO2)

• Primary drinking water treatment (disinfection

and odor control)

• Control of iron, manganese, and phenolic compounds
• More effective in presence of organic matter than chlorine
• Reduces formation of THM by-products (carcinogens)
• Maximum residual disinfection limit (MRDL)= 0.8 ppm
• Rapidly breaks down to chlorite, chlorate, and chloride

Process Solutions

Uses of Chlorine Dioxide - ClO2

• Sanitizers: Many EPA registered products
• For hospital, food and non-food applications including: HVAC

systems, animal containment areas

• Additives/deodorizers:
• Low levels found in toothpastes, mouthwash, deodorizers, consumer

cleaning solutions

• Enerfab and Purdue have been working on research with

Gaseous chlorine dioxide since 1996 for food industry applications

• Aseptic equipment sterilization
• Direct sanitation of produce surfaces (reduce E. coli, Salmonella, Listeria)

Process Solutions

Chlorine Dioxide - ClO2

GAS versus AQUEOUS FORMS GAS

• Pure chlorine dioxide depending on generation method
• Most commonly stripped from aqueous solutions

Aqueous

• Gas dissolved in water
• Typically generated by mixing sodium chlorite with acid
• Not very stable, off-gasses ClO2 when open to atmosphere
• Breaks down over time to chlorite and chloride

Stabilized Chlorine Dioxide

• Aqueous solution of sodium chlorite and high pH buffer
• (MUST BE ACTIVATED PRIOR TO USE)

Process Solutions

Generation Methods

Chlorine gas + sodium chlorite solution Chlorine gas + technical grade sodium chlorite flakes Hydrochloric acid + sodium chlorite solution Hydrochloric acid + hypochlorite + sodium chlorite solution Hydrogen peroxide + sulfuric acid + sodium chlorate solution Electrolysis: Electricity + sodium chlorite solution

Process Solutions

GAS Aqueous

An EPA laboratory bus circles the Hart building to monitor the air for gas leaks Postal Office Decontamination in Hamilton Township, NJ

Chlorine Dioxide and Anthrax

2001 2002

Chlorine Dioxide - Safety

• Irritates eyes, nose, and respiratory system
• (burning sensation)
• OSHA 8-hour Permissible Exposure Limit (PEL) 0.1 ppm
• Short-term exposure limit (STEL) 0.3 ppm (15 min)
• Safety Monitors Required around facility
• Gas must be generated on-site at time of use
• Gas can be explosive in air above 10% concentrations***

*** Enerfab generation method creates 4 % maximum concentration

Process Solutions

Chlorine Dioxide - Registrations

EPA/FDA Registrations:

• First registered as aqueous disinfectant/sanitizer (1967)
• Many approved aqueous applications (food & non-food)
• Gas form registered as a sterilant (1988)
• Gaseous ClO2 registered as a sterilant for

manufacturing/processing equipment, surfaces, tools, and clean rooms

Process Solutions

Chlorine Dioxide in the Food Industry

Process Solutions

• The Code of Federal Regulations (21 CFR 173, FDA) currently

allows the use of chlorine dioxide for numerous food processing applications at various concentrations.  Up to 3 ppm chlorine dioxide in water may be used to wash fruits and vegetables followed by a potable water rinse, or further processing.  Also approved for controlling microorganisms in process water contacting fresh poultry carcasses.  Fogging potatoes in storage

• The Code of Federal Regulations (40 CFR 180.940) also allows the

use of chlorine dioxide as a terminal food equipment sanitizing solution at levels of 100 – 200 ppm in water. (also found in 21 CFR

178.1010)

Chlorine Dioxide Gas Generation

Enerfab Generation Process: ClO2 Generated by Flowing Chlorine Gas Through Sodium Chlorite Canisters

2NaClO2 + Cl2  2ClO2 + 2NaCl

2% Chlorine Gas Generates 4% Chlorine Dioxide

2 % Chlorine Gas Process Vessel

• r Treatment chamber

Sodium Chlorite

Process Solutions

(Guaranteed to be Below Explosive Limit of 10 %) 2 % Cl2 4 % ClO2 Solid Sodium Chlorite flakes

MOLDS: Aspergillus niger, Penicillium citrium, BACTERIA: Leuconostoc mesenteroides, and Lactobacillus buchneri Both commonly found in citrus juices Time to kill 90 % of organisms on stainless steel surfaces (below)

Chlorine Dioxide Effectiveness

Process Solutions

Log Reduction Time + standard deviation (minutes) ClO2 (mg/L)

MOLDS BACTERIA

L.buchneri

• L. mesenteroides
• P. citrium
• A. niger

0.3 13.2 ±2.7 12.6 ±2.6 7.2 ±1.2 10.8 ±1.8 0.5 12.1 ±2.0 12.3 ±1.5 5.1 ±0.4 8.6 ±0.6 1 11.6 ±1.5 11.0 ±1.3 2.4 ±0.2 6.2 ±1.0 2 10.2 ±1.1 9.2 ±1.3 0.8 ±0.1 3.3 ±0.6 z-value 18.6 12.6 1.7 3.4

Important Factors for Disinfection

• Concentration (mg/l)
• Contact time
• Purity
• Relative humidity (higher is better)
• Surface: stainless, paper, Munkadur (epoxy)
• Crevices
• Presence of liquid water (acts as a sink)

• Gas sterilization of pilot-scale aseptic processing line and surge tank
• Evaluated using Lactobacillus buchneri (106), in orange juice
• Gas concentration 1 mg/liter; relative humidity 85 %
• Gas circulated through 1 ½” stainless tubing around stainless tank

Chlorine Dioxide Research

Process Solutions

Results

• L. buchneri grown in orange juice

required 2 hrs to obtain sterility.

• Demonstrated that chlorine dioxide is

effective against microorganisms in a high acid environment.

• ClO2 is a broad-spectrum biocide (kills bacteria, yeast,

molds, and inactivates viruses)

• Bulk Aseptic Storage Requires a Commercially Sterile

Container

• Storage Tanks have been Historically Sterilized with

Iodophor, an effective but timely process

• Three Main Drivers Behind Use of Chlorine Dioxide

Reduction in Sterilization Time Reduction in Sterilization Cost Reduction in Water Usage

Process Solutions

Why Chlorine Dioxide?

Current Sterilization Technology

• Million Gallon Bulk Storage Tanks (high acid products)
• Flooded with 1 Million gallons of Iodophor at 25 ppm
• Steam sterilize Nitrogen Filter
• Requires 6 days for entire sterilization process.

Fill – 2.5 Days Seal Off – 1 Day

N2 Supply

N2 Filter Rupture Disk

Transfer – 2.5 Days

N2 Supply

N2 Filter

Rupture Disk

Process Solutions

1 M GAL

Chlorine Dioxide Tank Sterilization

• Performed at Ambient Temp
• Gas sterilization of N2 Filter
• Sterilization Time < 1 Day

Injection & Recirculation

N2 Supply N2 Filter

Rupture Disk

ClO2 Generator

Sterile H2O Filters H2O Supply

Sterile Rinse

N2 Supply N2 Filter

Rupture Disk

ClO2 Generator

Sterile H2O Filters H2O Supply

Drain

• Reduction in Utility Costs
• Reduction in Waste Water

Blower

Equipment for Bulk Storage Facilities

• A Bulk Aseptic Storage Facility with 1,000,000 Gallon

Tanks Sterilized with Chlorine Dioxide Gas

Chlorine Dioxide Generator

Chlorine Dioxide Equipment

Blower Filters Portable For Small Tank Sterilization

1. 98 % Reduction in Water Use

• 1,000,000 Gallons of Iodophor vs 18,000 Gallons of Sterile

Rinse Water

2. 90 % reduction in sterilization time

• 134 Hours for Iodophor Flood Sterilization vs 12 hrs for Chlorine

Dioxide Gas

3. 63 % reduction in sterilization cost**

• vs. Cost of 1,000,000 Gallons of Iodophor

** Does not include capital equipment costs

ClO2 Gas Sterilization Savings

Process Solutions

Chlorine Dioxide in the Citrus Industry

• 39 Aseptic Intermodal Containers Currently in Service

Sterilized with Chlorine Dioxide Gas Nearly 20,000,000 Gallons of Aseptic Product Transferred to Date

• Chlorine Dioxide has been Used to Sterilize Aseptic

Transfer Lines for Loading and Unloading of Aseptic Intermodal Containers

• Recently Commissioned Bulk Aseptic Storage Facilities

with Tanks as large as 1.5 million gallon capacity Sterilized with Chlorine Dioxide Gas

Potential Uses for Chlorine Dioxide

Bulk Tank Sterilization Process Line Sterilization Aseptic Transport Container Sterilization Microbial Control on Produce Surfaces Building Fumigation

Summary

Advantages

• Chlorine dioxide is effective for sterilization of bulk tanks
• Easy to generate at inherently safe levels due to

generation method

• Under proper generation conditions (i.e., no excess

chlorine)

• Biocidal properties are less influenced by pH than chlorine*
• ClO2 gas is more convenient (especially for large vessels)

than liquid sanitizers

• C1O2 gas sterilization results in considerable savings in
• perational cost, maintenance costs, and time

QUESTIONS?

Process Solutions